Silicone hydrogels have been the material of choice for a variety of applications including ophthalmic devices, wound dressing material, and as a drug release medium. Compatibilizing of hydrophilic and hydrophobic components within silicone hydrogel formulations is critical far the manufacturing of optically clear wettable contact lenses.
While patient comfort has driven the market use of contact lenses, the modality for use of these lenses depends on both the physical properties (including oxygen transport and lubricity of the lens) as well as the amount of protein and lipid deposition on the lenses during wear. In a silicone hydrogel contact lens the oxygen transport property which has been correlated to lens comfort can be successfully accessed by using designed silicone compounds while the wettability can be achieved by different methods of incorporation of hydrophilic components. Different technologies exist today to present a final lens that has the optical clarity and the desired wettability and lubricity, with controllable modulus and high oxygen transmissibility in the silicone hydrogel lenses.
Adsorption of unwanted components from the ocular tear fluid on to the lens material during wear is one of the contributory factors for causing reduced comfort experienced by patients. In addition, bacterial infections can potentially occur if lens care regimens are not followed for use of the lenses. The extent of undesirable adsorptions on the lens will determine the lens care needs for a specific lens and will impact on the duration the contact lens can be present in the eye.
Infection as a result of contact lens wear for prolonged periods of time partly due to improper use of lens care solution is not uncommon. While contact lens manufacturers have resorted to daily disposable lenses to limit this phenomenon, in order to minimize infection due to contact lens wear, drug release and/or release of antimicrobial components during contact lens wear is an attractive approach.